Anybody here older than time itself?

BobG

While I have to know quite a few different time scales, I never really paid much attention to when these were developed:

1967 - the second was officially defined as 9,192,631,770 cycles of radiation due to transition between the two hyperfine levels in the ground state of the isotope cesium 133. I guess this is the date of our modern definition of time.

1972 - The new definition of time didn't correlate very well to the Earth's motion, so a new compromise time scale using the official second was developed: Coordinated Universal Time (UTC). This adds a leap second every so often to sync up UTC to the Earth's motion (There's a problem with this. Sometimes it's done after 12 months; sometimes it's done after 18 months. Timing is so critical with modern computer networks, no one wants to depend on humans to all manually adjust their clocks by one second when they're supposed to, so we haven't added a leap second since Jan 1, 1999. If we don't fix this urgent problem within a few thousand years, we'll be going to work when the sun sets and getting home when the sun rises).

This, worst of all:

Ephemeris Time was established in 1960. It went obsolete in 1984, being replaced by Terrestrial Dynamic Time, which was developed in 1977. Time scales have been born and died during my lifetime. AAAUGHHH!

I could add other time scales added during the last 30 years, but I think Chicago's on the radio, "Does anybody really know what time it is? Does anybody really care?"

On a less disturbing note, anybody know when the longest solar day of this year will be?

Smurf

Thats.....interesting.....
I wonder if any more will be invented and go obsolete within my life time.

jimmy p

Isn't it supposed to be 21st of June?

franznietzsche

sometimes its the 22, but yes,its thereabouts. The summer solstice. Shortest day of the year is two days before christmas, methinks, althoughchristmas issupposed to be the wintersolstice (early catholic church had the strategy of replacing pagan holidays with its own).

BobG

You guys are missing the point, especially if you live in Australia.

One solar day is measured from local noon (Sun at zenith) to local noon. It has nothing to do with how much daylight there is that day.

check

I wouldn't mind a metric time. 10 hrs/day, 100 minutes/hr, 100 sec/min... Just make the length of a second sone 20% shorter or something like that :)
Yeah, ok, it's silly... I'll go away now.

selfAdjoint

My idea would be to use dimensionless time, fractions of 2pi for uniform time, and then express solar time by a function. Get people used to it, since it's the common way in astronomy.

Gokul43201

I am older than time itself.

When I was born, day and night hadn't been separated yet.

No, wait...that's not me...sorry.

Moonbear

Oh yeah, try telling a country that wouldn't even switch from imperial to metric units to start telling time in 2pi fractions.

Smurf

No one said anything about the states, the scientific community in the US isn't exactly growing. The USA will remain the odd ball out after the rest of the world has advanced to the 2pi quantum age untill it falls to internal revolt.

BobG

Odd ball out? Liberia and Burma still use the English system. That's a total of three countries in the world that still use the English system. I think that qualifies as.... as..... as..... well, at least a trio.

Gokul43201

Burma ? Burma ? Ha ha. Only an American would refer to Myanmar by this archaic name.

Smurf

No, Bob's right. We should definitly hold the United States of America to the same standards as some of the smallest, poorest, least inhabited countries in the world.

BobG

The answer is Dec 23.

The Earth rotates at a constant angular velocity. If the Earth's orbit were perfectly circular and the equator were lined up with the Earth's orbital plane around the Sun (the ecliptic plane or "plane of the Solar System"), every solar day would be the same length.

As it is, the Earth's orbit is slightly elliptical. The center of the Earth is moving faster at perigee (when it's closer to Earth). That means the Earth has to rotate further to get from one local zenith to another. Solar days at perigee are generally longer than solar days at apogee, when the Earth's motion around the Sun is slower. Perigee occurs the first week of January and apogee occurs the first week of July (that's why Northern Hemisphere seasons are milder than Southern Hemisphere seasons).

The tilt of the Earth changes the length of the solar day as well. Solar days are shorter at spring and fall when poles are perpendicular to the line between the Earth and Sun. Solar days are longer the further away from the Sun that the poles are pointing or the closer to the Sun that the poles are pointing. Those dates correspond to the equinoxes and solstices.

The end result is the longest solar day is close to the winter solstice, but skewed a bit towards the date of perigee, or December 23 and lasts about 24 hours and 30 seconds. The shortest solar day occurs a little before the autmumnal equinox on September 17 and lasts about 23 hours, 59 minutes, and 39 seconds.

Gokul43201

Nice one. Most folks interpreted the question as "the day with the most daylight hours".

Tsu

If the US can't get the hang of temperature in Centigrade or lengths in meters, how can we be expected to get used to a change in time?!?! :rofl